from The Century Dictionary and Cyclopedia

Proceeding from a conscious or unconscious internal impulse; occurring or done without the intervention of external causes; in a restricted sense, springing from one's own desire or volition, apart from any external suggestion or incitement.

Growing naturally, without previous human care.

Growing as native; indigenous.

In biology, instinctive or automatic, as some actions of animals which depend upon no external stimulus and are performed without apparent motive or purpose; uninfluenced by external conditions, as a change in structural character. Compare spontaneity, 2.

from Wiktionary, Creative Commons Attribution/Share-Alike License

Examples

Thus, the term spontaneous order may be used to refer strictly to voluntary orders — that is, forms of social coordination which emerge from the free actions of many different people, as opposed to coordination that arises from some people being forced to do what other people tell them to do.

We think that when we deal with medicine in brain first, the real source of what he calls spontaneous healing is brain chemistry, and that when we change brain chemistry, we change the mind and facilitate these spontaneous healings and transformations of human health.